Electric discharge lamp



M. PlRANl ELECTRIC DISCHARGE LAMP Filed July 15, 1929 ms ATTORNEY Sept. 27, 1932.

' Patented Sept. 27, 1932 UNITED STATES PATENT OFFICE MABCELLO PIRANI, OF BEBLIN-WILHERSDORF, GERMANY, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK ELECTRIC DISCHARGE LAMP Application filed July 15, 1929, Serial No. 378,471, and in Germany July 14, 1828.

Heretofore, in electric discharge lamps with gas or vapor filling and with a View to obtaining a steady burning, or to obtaining another light color, and preferably a white light color, of the gas or vapor discharge, it has been proposed, among other things, to mount in the interior of the lamp chamber for the guidance of the "as or vapor discharge, a tubular body of insulating material, such as refractory oxides, which was supposed to be raised to a. red heat by the discharge and thus cause the desired light radiation. The placing of such a guide tube light emitter in the discharge path, however, has been found very inefficient as the guiding tube absorbs or shuts off all or most of the light from the gas or vapor discharge. Furthermore, because of the relatively small dielectric strength of such material it is not possible to build up the current density of the discharge high enough to attaln the desired results.

The use of metallic, conducting, solid walled hollow bodies for the hitherto used insulating material making up the guiding hollow body has hitherto never been tried, for the opinion was that the light column would break in such a current conducting hollow body, and also that the current conductor used would only be brought to a red heat.

l have discovered, however, that the foregoing opinion is not correct and that the positive column of the discharge, probably under the influence of the wall charge, goes freely through a current conductor and particularly a metallic hollow body.

lfn my new device using a solid wall hollow body of current-conducting, high melting point material, in particular a metal having a high melting point, since dielectric strength naturally does not come in question, increased current density and therewith increased light density are obtained in the operation of the device. Also any suitable high melting point metal, such as tungsten, can be used for the solid walled hollow body, as it can easily be made of uniform wall strength and in particular also of perfectly uniform thickness over its entire length, while with a hollow body consisting of innot hitherto been attained in previous devices and perfect uniformity of surface brightness is now attained for the first time and which is very essential for the use of such lamps as projection means and for crack or slot illumination.

A more essential advantage, in particular a much smaller light absorption takes place, if the new conducting guiding hollow body is provided with holes or perforations throughout its entire length. Such a sievelike conducting hollow body allows not only a large part of the light from the gas or vapor discharge to go out unhindered through the openings, but also is itself charged with perfect uniformity in all its parts by virtue of its good conductivity when the lamp is put into operation. In regard to the electrically charged mesh of the hollow body, it is probable that a space charge is created which prevents the transfer of the gas or vapor column through the openings of the hollow body. Thegas or vapor discharge is thus positively confined within the hollow body, and also in a narrow space therein. This, in connection with the high heat durability of the hollow body, permits the current density of the discharge to be raised Very high.

Finally, as the perforated current conducting hollow body by virtue of its essentially small radiating surface has only a small heat radiating loss, thus it follows that with an equivalent applied current an extremely higher current. density of the discharge is secured.

The new perforated and conducting hollow body can consist of thin metal plates with punched perforations or of crossed bands or wire, it can furthermore be in the shape of cylinders or prisms. The openings or mesh of the conducting hollow body must at least make u or of the surface of the hollow .100 y, so that the light of the discharge is covered as little as possible, and the openings should be very small and arranged close together, so that small light arcs cannot be formed.

In addition to the foregoing, by the use of a hollow body in a tube shape made of a mesh of molybdenum or tungsten wire net or correspending wire web, only about 10% to 20% of the light of the gas or vapor column is hidden from view and therefore a higher temperature equilibrium is very easily produced and maintained.

In the drawing is shown in Fi 1 an embodiment in section of the new e ectric discharge lamp, and,

Figs. 2 to 6 show alternative embodiments of 1216 gas or vapor column hollow body guide tu s.

Referring to Fig. 1 at both ends of a suitable cylindrical chamber 1 is one of the current leads 2, 2, sealed into the base tubes 3, 3. The interior ends 5 of the current leads from the pinched seal 4 are led through the protectmg tubes 6 and attached to a tungsten or an iron alloy electrode stem, 7. Each electrode stem goes over into a thickened head stem 8, in which is countersunk a body 9, which consists of a material which will assure the establishing of the arc and also a good electron emission. Each of the electrode bodies is surrounded by a chamber 10 consisting of a mass of quartz or else a ceramic material such as magnesium oxide, possessing the two neck parts 11, 11. To the short, flange shaped neckpart 12 of the quartz chamber 10 is, by means of s ipover part 15, made of nickel, molybdenum or other suitable material, connected to tube 16, made of tungsten wire net, which guides the current dischar e of the gas or vap or column between the e ectrodes 8, 9, 8 9. he discharge chamber can contain in t e usual manner common gas, for example nitrogen or carbonic acid as, or else rare gas, for example neon, heium, or argon, or also a mixture of common gases and rare gases. Also a va or evolvlng metal can be used, for examp e, mercury, either in an offset to the discharge chamber, or in place of one solid electrode or even of both solid electrodes. In order that the current circuit, the discharge of which is confined in the interior of net tube 16, may not flow over an electrode part 7 and from there to the current conducting wires 5 emerging from pinch part 4, these parts are enclosed by shell 17, made of quartz or ceramic material, which is located between neck parts 11 of the quartz chambers 10 and base tubes 3, and which reaches up to electrode bodies 8.

A wire web can be used as the guide of the gas or va or column in place of the perforated an conducting hollow body. The

wires of such web can consist of non-conducting oxide rare earths, for example, thorium oxide, cerium oxide, or scandium oxide which is made conductive by adding through 1m- Laredo pregnation molybdenum or other high meltm point material.

11 lace of the net tube shown in Fig. 1, that s own in Fig. 2 can be used, which consists of several parallel spaced apart wires 18, over wh1ch are wires 19, all wires made of a metal having a high melting point or an equivalent material.

As is shown also, in Fi 3, a number of wires 20 made of diflicu tly fusible metal are supported by suitable spiral wires 21.

The perforated conducting hollow body also, as ,F1 4 shows, can be covered with a very thin llght permeable heat resisting foil 22 made of suitable difiicultly fusible metal. The latter makes it possible to use also a net or web with a proportionately larger mesh, without the rlsk of the discharge column passm through the mesh of the hollow body. A so by the use of such a metal foil the color of the emitted rays of lightbecome advanta eously influenced.

f it is desired, a cell is placed in the crforated hollow body which gives a high llght intensity, then the hollow body is made narrow, and this can be accomplished, as shown in Fig. 5, by mounting centrally a perforated d1sk 23 in the interior of the said net shaped hollow body 16.

With a hlgher current load and because of the hi her current density of the discharge, the ho low body of suitable tungsten wire net 1s heated to an intense white heat. This permits the attaining by the use of a luminescent mercury vapor column of strong ultraviolet radiatlons, and by the visible and ultra-red radiations from the tungsten, of a collection of rays which possess a high therapeutic value. If it is desired to make use of the invisible rays, the lamp chamber 1 must naturally be made of quartz, uviol glass or else consist of other glass permeable to these e electrodes may also be made in other ways with the leads attached thereto; for example, they can, as shown in Fig. 6 consist of shell 24 slipped over the pinched part 4 of the base tube 3, said shell 24 consists of magnesium oxide or other high quality insulation materlal, and giving support to the insulation plate 25 on which rests the electrode body 8.

III

In the glass tube 3 is sealed the current lead wire 5 which is led up through the opening 20 of the electrodebody 8 and made fast to the upper side thereof. The current lead wire 3 over its entire length between the electrode body 8 and base tube pinched part 4 is enclosed by a tube 27 made of suitable materi can be made in other ways. For example, 1t can be an incandescent 30 filament electrode or else an electrode may be used which evolves gas in operation.

I claim:

1. In an electric discharge lamp, a container, electrodes sealed therein, a gaseous filling therein, an interposed tubular bod of conducting material surrounding the discharge path between the electrodes and enclosing chambers for said electrodes joined to said tubular body.

2. In an electric discharge lamp, a container, electrodes sealed therein, a gaseous filling therein, an interposed tubular body of conducting material surrounding the discharge path between the electrodes, said tubular body being provided with small openings over its entire length and enclosing chambers for said electrodes joined to said tubular body. 7

3. In an electric discharge lamp, a container, electrodes sealed therein, a gaseous filling therein, an interposed tubular body of conducting material surrounding the discharge path between the electrodes, said tubular body consisting of wire mesh and enclosing chambers for said electrodes joined to said tubular body.

4. In an electric discharge lamp, a container, electrodes sealed therein, a aseous filling therein, a tubular body oi con ucting material surrounding the dischargepath between the electrodes, said tubular body consisting of wire mesh comprising electrically non-conducting and conducting materials and enclosing chambers for said electrodes joined to said tubular body.

5. In an electric discharge lamp, a container, electrodes sealed therein, a gaseous filling therein, an interposed tubular body of conducting material surrounding the dis charge path between the electrodes, said tubular body consisting of spiralled wire mounted on paralleled supports and enclosing chambers for said electrodes joined to said tubular body.

6. In an electric discharge lamp, a container, electrodes sealed therein, a gaseous filling therein, and a tubular body of conducting material surrounding the discharge path between the electrodes, and a thin light giiflusing metal foil mounted on said tubular 7. In an electric discharge lamp, 9. container, electrodes sealed therein, a gaseous filling therein, and a tubular body of conducting material surrounding the discharge path betweenthe electrodes, and an annular disk in said tubular body.

8. In a positive column electric discharge lamp, a container, electrodes sealed therein, a gaseous atmosphere therein, a tubular body of conducting material surrounding the dis charge path between the electrodes and enclosing chambers for said electrodes joined to said tubular body.

MARGELLO PIRANI.

, between the electrodes, said tuy bular body being 

